Testborer



*May .5, 1958 I J. L. BARRETT ETAL 2,833,120

TESTBORER Filed April 5, 195e `ilnited States Patent O TEsrBoRER .lames L. Barrett and Richard ,G.`Parse, Pittsburgh, Pa.,

assignors to Pennsylvania Drilling Company, Pittsburglr, Pa., a corporation of Pennsylvania Application April 5, 1956, Serial No. 576,272

4 claims. (c1. si- 73) This invention relates to a device for driving testbores into the earth by means of a gravity-operated drive hammer.

To determine the geological and physical Ycharacteristics of a soil it is necessary to conduct sub-surface exploration. One of the most common methods of doing this is to take drive samples, which is doneby driving a casing or pipe into the soil. v i

One purpose of driving a testbore is to determine the density of diierent strata of the earth. This is done by determining the number of blows needed to drive the tool one foot into the earth. It is important that every blow be of the same magnitude, and the present invention obtains this result by providing for a free fall of the driving l hammer a1; all speeds of the rig.

This object is achieved by attaching one end of the operating cable to the drive hammer, and the other end of the cable to the drive head on the sampling tube. A bight of the cable is passed over a reciprocable pulley, which raises the hammer a predetermined distance, and then permits it to drop by gravity. Due to the attachment of the cable to the drive head, the distance through which the hammer is raised remains constant for each stroke of the hammer, thus insuring that each hammer blow will have exactly the same force.

The reciprocable pulley is `moved by a cam, or other device, which causes it to move a pre-determined distance on each stroke, and then releases it to permit the hammer to fall by gravity. This arrangement permits the hammer to be operated very slowly, while obtaining a free gravity fall on each stroke.

These, and other objects and advantages of the invention will become apparent as the description proceeds.

In the drawings:

Fig. 1 is a vertical view, partly in section and partly diagrammatic, illustrating the invention.

Fig. 2 is a partial plan view illustrating the cam and lifting lever of the device of Fig. l.

Referring to the drawings more particularly, it will be :seen that the portable tower A is mounted on one end of a wheeled vehicle B. The gravitybperated drive hammer C is used to drive the casing D into the ground.

The operating cable 10 is attached at one end to the drive hammer C; fromV thence it passes over a sheave 11 at the top of the tower A; it then passes downwardly around an idler sheave 12 which is fixed in the frame of the vehicle B; thence passes around the reciprocable sheave 13; thence around idler sheaves 14 and 15 and thence to a point of attachment with the drive head 16 which is connected to the casing D.

The reciprocable sheave 13 is mounted on one end of a drive arm 17 which has its other end pivoted on shaft 18. Intermediate its ends the drive arm 17 is provided with a roller 19. A cam arm 20 is mounted on shaft 21 and is arranged to periodically engage the roller 19. Suitable l i 2,833,120 l Ice Patented May 6, 19578 material, such as steel .cable which has a substantially constant length. The portion of the cable which extends over the reciprocable sheave 13 is in the form of a bight and when the sheave 13 is moved upwardly, this bight is lengthened thereby shortening the effective length of the cable, and raising the drive hammer C.

The parts are so arranged that during the rotation of the cam arm 20it engages the roller 19 thus lifting the'outer end of the 'drive 'arm 17 which carries the reciprocable sheave 13. After cam arm 20 passes roller 19, the outer end of drive arm 17 is permitted to fall back to its lower position, which may be determined by suitable stop means. It will be understood that as soon as the cam arm clears the roller 19, the lever arm 17 will fall without hindrance and will thus permit' the drive hammer C to fall by `gravity to deliver a blow on the drive head 16.

It should be pointed out that the cam arm 20 may be rotated very slowly while still permitting an unimpeded gravity fall of the drive hammer. This slow operation of the cam will make it easy to count accurately the number of hammer blows delivered to the drive head 16.

It will be clear that with this construction, the distance between the drive hammer C and the drive head 16 remains constant even as the casing D is driven into the ground. This is because yof the fact that the length of the operating cable 10 is constant; the relationship of the ditferent sheaves is constant and the lower end of the cable is attached directly to the drive head. The result is that while the drive head 16 is driven downward by a particular blow of the drive hammer C, on the next stroke the top position `of the drive hammer C will be lower than its .top position on the previous stroke by a distance equal to the distance the drive head has been driven downwardly. The result is that on each stroke, the drive hammer C is raised exactly the same distance above the drive head 16 and hence the force of each blow of the drive hammer is exactly the same.

'Ihus if the hammer is of a specied weight (usually 140 lbs.) and is `dropped through a specified distance (usually 30 in.) each blow on the sampler will have exactly the same known force.

Drive sampling is =a very practical land economical method of obtaining a soil sample and determining the bearing capacity or penetration resistance of the formation being tested. In order to obtain accurate results it is necessary to know the exact number of blows required to drive the sampling tube a definite distance, as well as the exact force of each blow. A record of the number of lblows required to advance the sampler one foot into the formation, is recorded, and this record can be interpolated into the relative density and consistency of the material.

'Ihe present invention provides an automatic driverwhich eliminates the physical labor of driving with a conventional drum or cathead, and also permits an increase in the rate of drilling. This is due to the fact that the automatic driver insures a uniform force resulting from each drop of the hammer, regardless of the speed of operation of the rig.

While the means for lifting the drive hammer C is preferably a wire cable, it should be understood that other equivalent exible means, such as a chain, could be employed.

It should also be understood .that the sheave 13 could be reciprocated by other means and in other directions. For example, it could be reciprocated horizontally in stead of vertically. Also, more than one of the sheaves could be reciprocated if desired.

According to the provisions of the patent statutes, we have explained the principle of our invention and have illustrated and described what we now consider to represent its best embodiment. However, we desire to have it understood that, within the scope of the appended claims,

3 Y the invention may be practiced otherwise than as specifically illustrated and described.

We claim:

1. An earth-testing machine of the `type in which a 1too1 is driven into the earth lby the gravity action `of `a drive hammer, Athe hammer being raised by `a single cable which passes `over a .sheave mounted on a tower, the improvement which comprises: vone endof the cable being fastened to the hammer, and the other endl of thecablebeing fastened to `the upper endof the tool which is being driven into the earth, the cable beingl formed of non-stretchable material, so that its length remains substantially constant, a series of sheaves, at least one of which is recip- -rocab1e, the intermediate portion of the cable being `led over the series of sheaves, means operable to reciprocate the reciprocable `sheave to` raise the drive hammer, and operable to release said reciprocable sheave to permit -the drive hammer to fall by gravity, whereby the successive gravity blows of the drive hammer on theV `tool `are of the same magnitude, regardless of movement of the tool into the earth.

2. A device as specified in claim 1 in which theoperable tool is driven into the earth by the gravity action of a drive hammer, the hammer being raised by a single flexible element which passes over va tower, the improvement which comprises: one end of the exible element being fastened to the hammer, and the other end of the exible elementbeing fastenedto the upper end of the tool, the exible element being formed of non-stretchable material, so that its lengthremains substantially constant, and operating means to operate the hammer, said operating means Vincludingua. reciprocable sheave` over which a bight ofthe ,flexible element is passed and means to reciprocateV the sheave, to' raise the hammer and to permit it to fall bygravity, vwhereby the successive blows of the hammer on the tool are of the same magnitude, regardless of movement of the tool into the earth.

4., A device als specified in claim 3 in which `the flexible element is a steel cable.

References Citedin the le of this patent UNITED STATES PATENTS 42,038 Wood Mar. 22, 1864 1,034,675 `Baldwin Aug. 6, 1912 2,157,951 Buschman May 9, 1939 

